De-duplication aware secure delete

ABSTRACT

A mechanism is provided in a data processing system for de-duplication aware secure delete. Responsive to receiving a secure delete request for a file, the mechanism identifies a list of file blocks to be securely deleted from a physical disk device. Responsive to determining at least one virtual block of another file refers to a given disk block corresponding to a file block in the list, the mechanism copies the given disk block to generate a copied disk block in the physical disk device and updates a pointer of the at least one virtual block to refer to the copied disk block. The mechanism writes a secure delete pattern for each file block in the list of file blocks to a disk block in the physical disk device without performing de-duplication processing.

BACKGROUND

The present application relates generally to an improved data processingapparatus and method and more specifically to mechanisms forde-duplication aware secure delete.

Data de-duplication is a storage concept where redundant data areeliminated to significantly shrink storage requirements and improvebandwidth efficiency. Data de-duplication is a specialized datacompression technique for eliminating duplicate copies of repeatingdata. The technique is used to improve storage utilization and can alsobe applied to network data transfers to reduce the number of bytes thatmust be sent. In the de-duplication process, unique chunks of data, orbyte patterns, are identified and stored during a process of analysis.As the analysis continues, other chunks are compared to the stored copyand whenever a match occurs, the redundant chunk is replaced with asmall reference that points to the stored chunk. Given that the samebyte pattern may occur dozens, hundreds, or even thousands of times, theamount of data that must be stored or transferred can be greatlyreduced.

In the de-duplication process, duplicate data is deleted, leaving onlyone copy of the data to be stored. This single copy is called the mastercopy, and in place of the deleted copies (secondary copies) the filesystem keeps a reference pointer, which points to the master copy. Whende-duplication is performed on in-band traffic, it is referred to asin-line de-duplication.

Secure delete, also referred to as data clearing or data wiping, is asoftware-based method of overwriting data that completely destroyselectronic data residing on a hard disk drive or other digital media.Unlike degaussing and physical destruction, which render the storagemedia unusable, secure delete techniques remove all information whileleaving the disk operable, preserving information technology (IT) assetsand environment.

Software-based overwriting uses software applications to write patternsof random meaningless data onto all of a hard drive's sectors. Centerfor Magnetic Recording Research (CMRR) defines a set of standards forsecure delete on disk devices. Secure delete of a file requiresperforming multiple writes of the patterns on the file blocks. Thesewrites must be performed directly on the physical device.

SUMMARY

In one illustrative embodiment, a method, in a data processing system,is provided for de-duplication aware secure delete. The method comprisesresponsive to receiving a secure delete request for a file, identifyinga list of file blocks to be securely deleted from a physical diskdevice. The method further comprises responsive to determining at leastone virtual block of another file refers to a given disk blockcorresponding to a file block in the list, copying the given disk blockto generate a copied disk block in the physical disk device. The methodfurther comprises updating a pointer of the at least one virtual blockto refer to the copied disk block. The method further comprises writinga secure delete pattern for each file block in the list of file blocksto a disk block in the physical disk device without performingde-duplication processing.

In other illustrative embodiments, a computer program product comprisinga computer useable or readable medium having a computer readable programis provided. The computer readable program, when executed on a computingdevice, causes the computing device to perform various ones of, andcombinations of, the operations outlined above with regard to the methodillustrative embodiment.

In yet another illustrative embodiment, a system/apparatus is provided.The system/apparatus may comprise one or more processors and a memorycoupled to the one or more processors. The memory may compriseinstructions which, when executed by the one or more processors, causethe one or more processors to perform various ones of, and combinationsof, the operations outlined above with regard to the method illustrativeembodiment.

These and other features and advantages of the present invention will bedescribed in, or will become apparent to those of ordinary skill in theart in view of, the following detailed description of the exampleembodiments of the present invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention, as well as a preferred mode of use and further objectivesand advantages thereof, will best be understood by reference to thefollowing detailed description of illustrative embodiments when read inconjunction with the accompanying drawings, wherein:

FIG. 1 depicts a pictorial representation of an example distributed dataprocessing system in which aspects of the illustrative embodiments maybe implemented;

FIG. 2 is a block diagram of an example data processing system in whichaspects of the illustrative embodiments may be implemented;

FIG. 3 is a block diagram of a server integrated with a de-duplicationengine in which aspects of the illustrative embodiments may beimplemented:

FIGS. 4A and 4B are block diagrams illustrating a server performingsecure delete with data de-duplication in which aspects of theillustrative embodiments may be implemented;

FIG. 5 illustrates a de-duplication information table in accordance withan illustrative embodiment;

FIG. 6 illustrates an ignore block list data structure in accordancewith an illustrative embodiment:

FIG. 7 is a flowchart illustrating operation of a mechanism for startinga secure delete in accordance with an illustrative embodiment;

FIG. 8 is a flowchart illustrating operation of a mechanism forperforming a block write at the de-duplication engine in accordance withan illustrative embodiment; and

FIG. 9 is a flowchart illustrating operation of a mechanism formaintaining a de-duplication information table and an ignore list tableat an end of the secure delete operation for the file in accordance withan illustrative embodiment.

DETAILED DESCRIPTION

The illustrative embodiments provide a mechanism to make ade-duplication engine aware of a secure delete write for file blockssuch that secure delete write blocks will not be considered for thede-duplication process. The mechanism then performs these writesdirectly on the physical disk blocks. In the de-duplication table, fithe given disk blocks are already referred by the blocks belonging tosome other files, the mechanism creates a separate copy of the blocks.In this case, the de-duplication engine can inform the secure deletelogic about the copied blocks.

The illustrative embodiments provide a mechanism where on the securedelete request of the file, the secure delete logic communicates withthe de-duplication engine for special consideration of the file blocks.The mechanism may duplicate blocks within the file to be secure deleted.The de-duplication engine identifies a list of unique disk blocks forthe file. If a given disk block is referred by another file block, themechanism assigns a new disk block for other file blocks referring tothe current disk block. The de-duplication engine may maintain a blockignore list data structure to avoid de-duplication processing on theidentified disk blocks.

In one embodiment, the secure delete procedure can mark an ignored blockwith a special flag. Once all pointers of that block are removed/freed,the mechanism may add that block to the free block list. Before addingto the free list, the mechanism may check the special flag. If the flagis marked, the secure delete procedure can be performed on that diskblock, and the block will be added to the free list.

The illustrative embodiments may be utilized in many different types ofdata processing environments. In order to provide a context for thedescription of the specific elements and functionality of theillustrative embodiments, FIGS. 1 and 2 are provided hereafter asexample environments in which aspects of the illustrative embodimentsmay be implemented. It should be appreciated that FIGS. 1 and 2 are onlyexamples and are not intended to assert or imply any limitation withregard to the environments in which aspects or embodiments of thepresent invention may be implemented. Many modifications to the depictedenvironments may be made without departing from the spirit and scope ofthe present invention.

FIG. 1 depicts a pictorial representation of an example distributed dataprocessing system in which aspects of the illustrative embodiments maybe implemented. Distributed data processing system 100 may include anetwork of computers in which aspects of the illustrative embodimentsmay be implemented. The distributed data processing system 100 containsat least one network 102, which is the medium used to providecommunication links between various devices and computers connectedtogether within distributed data processing system 100. The network 102may include connections, such as wire, wireless communication links, orfiber optic cables.

In the depicted example, server 104 and server 106 are connected tonetwork 102 along with storage unit 108. In addition, clients 110, 112,and 114 are also connected to network 102. These clients 110, 112, and114 may be, for example, personal computers, network computers, or thelike. In the depicted example, server 104 provides data, such as bootfiles, operating system images, and applications to the clients 110,112, and 114. Clients 110, 112, and 114 are clients to server 104 in thedepicted example. Distributed data processing system 100 may includeadditional servers, clients, and other devices not shown.

In the depicted example, distributed data processing system 100 is theInternet with network 102 representing a worldwide collection ofnetworks and gateways that use the Transmission ControlProtocol/Internet Protocol (TCP/IP) suite of protocols to communicatewith one another. At the heart of the Internet is a backbone ofhigh-speed data communication lines between major nodes or hostcomputers, consisting of thousands of commercial, governmental,educational and other computer systems that route data and messages. Ofcourse, the distributed data processing system 100 may also beimplemented to include a number of different types of networks, such asfor example, an intranet, a local area network (LAN), a wide areanetwork (WAN), or the like. As stated above, FIG. 1 is intended as anexample, not as an architectural limitation for different embodiments ofthe present invention, and therefore, the particular elements shown inFIG. 1 should not be considered limiting with regard to the environmentsin which the illustrative embodiments of the present invention may beimplemented.

FIG. 2 is a block diagram of an example data processing system in whichaspects of the illustrative embodiments may be implemented. Dataprocessing system 200 is an example of a computer, such as client 110 inFIG. 1, in which computer usable code or instructions implementing theprocesses for illustrative embodiments of the present invention may belocated.

In the depicted example, data processing system 200 employs a hubarchitecture including north bridge and memory controller hub (NB/MCH)202 and south bridge and input/output (I/O) controller hub (SB/ICH) 204.Processing unit 206, main memory 208, and graphics processor 210 areconnected to NB/MCH 202. Graphics processor 210 may be connected toNB/MCH 202 through an accelerated graphics port (AGP).

In the depicted example, local area network (LAN) adapter 212 connectsto SB/ICH 204. Audio adapter 216, keyboard and mouse adapter 220, modem222, read only memory (ROM) 224, hard disk drive (HDD) 226, CD-ROM drive230, universal serial bus (USB) ports and other communication ports 232,and PCI/PCIe devices 234 connect to SB/ICH 204 through bus 238 and bus240. PCI/PCIe devices may include, for example, Ethernet adapters,add-in cards, and PC cards for notebook computers. PCI uses a card buscontroller, while PCIe does not. ROM 224 may be, for example, a flashbasic input/output system (BIOS).

HDD 226 and CD-ROM drive 230 connect to SB/ICH 204 through bus 240. HDD226 and CD-ROM drive 230 may use, for example, an integrated driveelectronics (IDE) or serial advanced technology attachment (SATA)interface. Super I/O (SIO) device 236 may be connected to SB/ICH 204.

An operating system runs on processing unit 206. The operating systemcoordinates and provides control of various components within the dataprocessing system 200 in FIG. 2. As a client, the operating system maybe a commercially available operating system such as Microsoft Windows 7(Microsoft and Windows are trademarks of Microsoft Corporation in theUnited States, other countries, or both). An object-oriented programmingsystem, such as the Java programming system, may run in conjunction withthe operating system and provides calls to the operating system fromJava programs or applications executing on data processing system 200(Java is a trademark of Oracle and/or its affiliates.).

As a server, data processing system 200 may be, for example, an IBM®eServer™ System P® computer system, running the Advanced InteractiveExecutive (AIX®) operating system or the LINUX operating system (IBM,eServer, System p, and AIX are trademarks of International BusinessMachines Corporation in the United States, other countries, or both, andLINUX is a registered trademark of Linus Torvalds in the United States,other countries, or both). Data processing system 200 may be a symmetricmultiprocessor (SMP) system including a plurality of processors inprocessing unit 206. Alternatively, a single processor system may beemployed.

Instructions for the operating system, the object-oriented programmingsystem, and applications or programs are located on storage devices,such as HDD 226, and may be loaded into main memory 208 for execution byprocessing unit 206. The processes for illustrative embodiments of thepresent invention may be performed by processing unit 206 using computerusable program code, which may be located in a memory such as, forexample, main memory 208, ROM 224, or in one or more peripheral devices226 and 230, for example.

A bus system, such as bus 238 or bus 240 as shown in FIG. 2, may becomprised of one or more buses. Of course, the bus system may beimplemented using any type of communication fabric or architecture thatprovides for a transfer of data between different components or devicesattached to the fabric or architecture. A communication unit, such asmodem 222 or network adapter 212 of FIG. 2, may include one or moredevices used to transmit and receive data. A memory may be, for example,main memory 208, ROM 224, or a cache such as found in NB/MCH 202 in FIG.2.

Those of ordinary skill in the art will appreciate that the hardware inFIGS. 1 and 2 may vary depending on the implementation. Other internalhardware or peripheral devices, such as flash memory, equivalentnon-volatile memory, or optical disk drives and the like, may be used inaddition to or in place of the hardware depicted in FIGS. 1 and 2. Also,the processes of the illustrative embodiments may be applied to amultiprocessor data processing system, other than the SMP systemmentioned previously, without departing from the spirit and scope of thepresent invention.

Moreover, the data processing system 200 may take the form of any of anumber of different data processing systems including client computingdevices, server computing devices, a tablet computer, laptop computer,telephone or other communication device, a personal digital assistant(PDA), or the like. In some illustrative examples, data processingsystem 200 may be a portable computing device that is configured withflash memory to provide non-volatile memory for storing operating systemfiles and/or user-generated data, for example. Essentially, dataprocessing system 200 may be any known or later developed dataprocessing system without architectural limitation.

FIG. 3 is a block diagram of a server integrated with a de-duplicationengine in which aspects of the illustrative embodiments may beimplemented. Server 300 includes a file system 302, block mapper 304,and de-duplication engine 306. File system 302 stores file 1 and file 2in physical disk device 310. Block mapper 304 maps file 1 to virtualblocks vblock0 and vblock1 and maps file 2 to virtual blocks vblock2,vblock3, and vblock4.

De-duplication engine 306 performs a hash on each virtual block andeliminates redundant data to shrink storage requirements and improvebandwidth efficiency. In the depicted example, de-duplication engine 306stores five virtual blocks vblock0, vblock1, vblock2, vblock3, andvblock4 as three disk blocks in disk device 310: disk block 0, diskblock 1, and disk block 2. The virtual blocks vblock0 and vblock2 havethe same hash; therefore, de-duplication engine 306 stores vblock0 asdisk block 0 and stores vblock2 as a reference to disk block 0. Thevirtual blocks vblock1 and vblock3 have the same hash; therefore,de-duplication engine 306 stores vblock1 as disk block 1 and storesvblock3 as a reference to disk block 1. De-duplication engine 306 keepsa de-duplication table (not shown in FIG. 3) to map disk blocks to hashvalues and referring virtual blocks. An example of a de-duplicationtable is shown in FIG. 5, described below.

Secure delete on a file is performed in multiple steps. In each step, aspecific pattern is written to every disk block of the file. For a writeoperation, de-duplication engine 306 computes a hash of the block in thewrite request. If the hash matches with any existing blocks, the virtualblock in the given write request will simply point to the existing diskblock and the write will not be performed on the disk.

FIGS. 4A and 4B are block diagrams illustrating a server performingsecure delete with data de-duplication in which aspects of theillustrative embodiments may be implemented. With reference to FIG. 4A,server 400 includes a file system 402, block mapper 404, andde-duplication engine 406. File system 402 stores a file in physicaldisk device 410. Block mapper 404 maps the file to virtual blocksvblock0, vblock1, and vblock2. De-duplication engine 406 performs a hashon each virtual block. In the depicted example, vblock0, vblock1, andvblock2 have different hashes and, therefore, are stored as separatedisk blocks: disk block 0, disk block 1, and disk block 2, respectively.

If a user is writing to vblockP, which is currently mapped to disk blockP, and its hash matches disk block M, currently referred by vblockM,then vblockP will point to disk block M, and disk block P will be freed.Thus, the write for vblockP will not be performed on the physical disk.This gives performance improvement as the number of disk writes isoptimized.

However, data de-duplication results in undesirable behavior for thesecure delete mechanism, where writes must go to the physical disks. Theproblem is with the secure delete implementation in the de-duplicationengine environment. As shown in FIG. 4A, the file has three virtualblocks mapped to three different disk blocks on the disk device 410.Turning to FIG. 4B, the secure delete mechanism writes a pattern onevery block of the file. For vblock0, the de-duplication engine 406generates hashP, and the de-duplication writes the pattern to disk block0 in disk device 410. For vblock1, because the write pattern isidentical, the de-duplication engine 406 generates the same hashP, andthe de-duplication does not perform a write to disk block 1. Rather, thede-duplication engine 406 will simply point to disk block 0 for vblock1,freeing disk block 1, which still contains the data to be securelydeleted. Similarly, for vblock2, de-duplication engine 406 generates thesame hashP, and disk block 2 is not securely deleted.

For secure delete on the file, only the first block, disk block 0, iswritten to disk with the write pattern. The remaining blocks, disk block1 and disk block 2, will simply be freed, leaving them in an insecurestate. In fact, for the first block, if the hashP value is matching withanother existing block for another file, then even the first block, diskblock 0, may not be written with the secure delete write pattern. Thus,the secure delete process does not perform its intended function.

One solution may be to bypass the de-duplication engine for securedelete writes. However, it is difficult to manage as disk blocks may bereferred to by other files. Bypassing the de-duplication engine andwriting directly to the disk device might corrupt data for thosereferring files. Another solution may be to have a separate storage forfiles that must be securely deleted. Because normal files and securedelete files can be part of the same file system or marked under thesame policy, it is difficult to manage separate secure delete storagefrom the file system layer. Also, at the time of creation, the usermight not be aware that a file must be securely deleted. This solutionalso results in inefficient usage of the storage space, as it eliminatesthe possibility of de-duplication across sets of files marked securedelete.

In accordance with an illustrative embodiment, a mechanism makes thede-duplication engine aware of the secure delete write for file blockssuch that the secure delete write blocks will not be considered for thede-duplication process. Writes for these blocks are performed directlyon the physical disk blocks. In the de-duplication table, if the givendisk blocks are already referred by blocks belonging to some other fileor files, then the mechanism creates a separate copy of the blocks. Inthis case, the de-duplication logic can inform the secure delete logicabout copied blocks.

FIG. 5 illustrates a de-duplication information table in accordance withan illustrative embodiment. This table contains an entry for each diskblock, with its state as allocated or freed, the hash value, and thelist of virtual blocks referring to this disk block. For any writerequest on a virtual block, the de-duplication engine computes a hash.If the hash matches with existing entries in the de-duplicationinformation table, the virtual block entry is added to the virtualblocks referring column, avoiding the need for a physical disk write. Ifno matching entry is found, the de-duplication engine searches thede-duplication information table for a free block, assigns the virtualblock to a free disk block, and updates the corresponding row of thetable with the hash value and virtual block referring, marking the diskblock as allocated. The server then performs a write for this virtualblock to the corresponding disk block on the physical device.

For a read request, the de-duplication engine refers to thede-duplication information table to identify the associated disk block.The server then performs the read operation on the identified diskblock.

The illustrative embodiments provide a mechanism where on a securedelete request, the secure delete logic communicates with thede-duplication engine for special consideration of the file blocks. Thiscommunication may be done either using a separate protocol channel, suchas remote procedure call (RPC), or a new command or using existingcommands, such as using reserved bits of a small computer systeminterface (SCSI) write command descriptor block (CDB). The mechanism mayduplicate blocks within the file to be secure deleted. Thede-duplication engine identifies a list of unique disk blocks for thefile. If a given disk block is referred by another file block, themechanism assigns a new disk block for other file blocks referring tothe current disk block. The de-duplication engine may maintain a blockignore list data structure to avoid de-duplication processing on theidentified disk blocks.

FIG. 6 illustrates an ignore block list data structure in accordancewith an illustrative embodiment. Each secure delete of a file will havea unique identifier (ID). The ignore block list includes an entry foreach disk block to be ignored by the de-duplication engine. Each entryincludes a secure delete ID for the secure delete operation affectingthe disk block and a list of the virtual blocks referring to the diskblock.

In one embodiment, the secure delete procedure can mark an ignored blockwith a special flag. Once all pointers of that block are removed/freed,the mechanism may add that block to the free block list. Before addingto the free list, the mechanism may check the special flag. If the flagis marked, the secure delete procedure can be performed on that diskblock, and the block will be added to the free list at an end of thesecure delete operation for the file.

As will be appreciated by one skilled in the art, the present inventionmay be embodied as a system, method, or computer program product.Accordingly, aspects of the present invention may take the form of anentirely hardware embodiment, an entirely software embodiment (includingfirmware, resident software, micro-code, etc.) or an embodimentcombining software and hardware aspects that may all generally bereferred to herein as a “circuit,” “module” or “system.” Furthermore,aspects of the present invention may take the form of a computer programproduct embodied in any one or more computer readable medium(s) havingcomputer usable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CDROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, in abaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Computer code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, radio frequency (RF), etc., or anysuitable combination thereof.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java™, Smalltalk™, C++, or the like, and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer, or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described below with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to the illustrativeembodiments of the invention. It will be understood that each block ofthe flowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions thatimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus, or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

FIG. 7 is a flowchart illustrating operation of a mechanism for startinga secure delete in accordance with an illustrative embodiment. Operationbegins (block 700), and the application sends a secure delete requestfor a given file (block 7001). The file system identifies a list of fileblocks for the secure delete and sends the list to secure delete logic(block 702). The secure delete logic sends the list of file blocks forsecure delete to the de-duplication logic (block 703).

The de-duplication logic identifies the list of unique disk blocks forsecure delete (block 704). This is the list of unique disk blocks in thephysical storage that must be added to the ignore list. For eachidentified disk block (block 705), the mechanism refers to thede-duplication information table to get the list of file blocksreferring to the disk block (block 706). The mechanism removes the diskblock from the de-duplication table (block 707). Then, the mechanismdetermines whether there are other files referring to the disk block(block 708). If there are no other files referring to the disk block,the mechanism determines whether the block is the last in the list ofblocks for secure delete (block 709). If the current block is not thelast block, operation returns to block 705 to consider the next block inthe list.

If there are other files referring to the disk block in block 708, themechanism gets a new free disk block indicated from the de-duplicationinformation table (block 710). The mechanism assigns the other fileblocks to the new disk block (block 711). Then, the mechanism copies thedata of the disk block to the new disk block (block 712). The mechanismthen determines whether the block is the last in the list of blocks forsecure delete (block 709). If the current block is not the last block,operation returns to block 705 to consider the next block in the list.

If the current block is the last block in block from the list in block709, then the mechanism adds the blocks to an ignore list with thesecure delete ID (block 713). Thereafter, operation ends (block 714).

FIG. 8 is a flowchart illustrating operation of a mechanism forperforming a block write at the de-duplication engine in accordance withan illustrative embodiment. Operation begins (block 800), and themechanism receives a block write request (block 801). The mechanismdetermines whether the block is in the ignore list (block 802). If theblock is not in the ignore list, the mechanism performs the regularde-duplication processing for the given block write request (block 803).Thereafter, operation ends (block 804).

If the block to be written is in the ignore list in block 802, themechanism ignores de-duplication processing for the block (block 805).The mechanism gets an associated disk block from the ignore list (block806). The mechanism then performs the write on the disk block directly(block 807). Thereafter, operation ends (block 804).

FIG. 9 is a flowchart illustrating operation of a mechanism formaintaining a de-duplication information table and an ignore list tableat an end of the secure delete operation for the file in accordance withan illustrative embodiment. At an end of the secure delete operation forthe file, operation begins (block 900), and the secure delete logicinforms the de-duplication engine with the secure delete ID (block 901).The de-duplication engine refers to the ignore list to get a list ofblocks associated with the secure delete ID (block 902).

For each disk block entry associated with the secure delete ID in theignore list (block 903), the mechanism calculates a hash value for thedisk block associated with the entry (block 904) and removes the entryfrom the ignore list (block 905). The mechanism then refers to thede-duplication information table and determines whether a matching hashexists (block 906). If a matching entry does not exist, the mechanismadds the entry as allocated in the de-duplication information table withthe hash value and the list of virtual blocks referring to the diskblock (block 907). Then, the mechanism determines whether the entry isthe last entry associated with the secure delete ID in the ignore list(block 908). If the entry is not the last entry, operation returns toblock 903 to consider the next disk block entry associated with thesecure delete ID.

If there is a matching entry in block 906, the mechanism adds allvirtual blocks referring to the disk block of the current entry to thevirtual blocks referring at the matching entry in the de-duplicationtable (block 909). The mechanism then adds the entry disk block as afree block in the de-duplication table (block 910). Then, the mechanismdetermines whether the entry is the last entry associated with thesecure delete ID in the ignore list (block 908). If the entry is not thelast entry, operation returns to block 903 to consider the next diskblock entry associated with the secure delete ID.

If the entry is the last entry associated with the secure delete ID inthe ignore list in block 908, then operation ends (block 911).

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

Thus, the illustrative embodiments provide a mechanism for performingde-duplication aware secure delete. Writes for secure delete areperformed directly to the physical disk blocks without de-duplicationprocessing. In the de-duplication table, if the given disk blocks arealready referred by blocks belonging to some other files, the mechanismcreates a separate copy of the blocks. The de-duplication enginemaintains an ignore list to avoid de-duplication processing of theidentified disk blocks. The secure delete mechanism then performsmultiple step pattern writes on the file blocks. For any block writerequest, the de-duplication engine checks if the write request is for ablock on the ignore list.

In one embodiment, the secure delete procedure can mark an ignored blockwith a special flag. Once all pointers of that block are removed/freed,the mechanism may add that block to the free block list. Before addingto the free list, the mechanism may check the special flag. If the flagis marked, the secure delete procedure can be performed on that diskblock, and the block will be added to the free list at an end of thesecure delete operation for the file.

As noted above, it should be appreciated that the illustrativeembodiments may take the form of an entirely hardware embodiment, anentirely software embodiment or an embodiment containing both hardwareand software elements. In one example embodiment, the mechanisms of theillustrative embodiments are implemented in software or program code,which includes but is not limited to firmware, resident software,microcode, etc.

A data processing system suitable for storing and/or executing programcode will include at least one processor coupled directly or indirectlyto memory elements through a system bus. The memory elements can includelocal memory employed during actual execution of the program code, bulkstorage, and cache memories which provide temporary storage of at leastsome program code in order to reduce the number of times code must beretrieved from bulk storage during execution.

Input/output or I/O devices (including but not limited to keyboards,displays, pointing devices, etc.) can be coupled to the system eitherdirectly or through intervening I/O controllers. Network adapters mayalso be coupled to the system to enable the data processing system tobecome coupled to other data processing systems or remote printers orstorage devices through intervening private or public networks. Modems,cable modems and Ethernet cards are just a few of the currentlyavailable types of network adapters.

The description of the present invention has been presented for purposesof illustration and description, and is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the art. Theembodiment was chosen and described in order to best explain theprinciples of the invention, the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A method, in a data processing system, forde-duplication aware secure delete, the method comprising: responsive toreceiving a request for a secure delete operation for a file,identifying a list of file blocks to be securely deleted from a physicaldisk device, wherein identifying a list of file blocks to be securelydeleted comprises creating one or more entries in an ignore list,wherein each entry in the one or more entries stores a secure deleteidentifier associated with the secure delete request, a disk blockidentifier of a corresponding disk block in the physical disk device,and one or more virtual blocks of the file referring to thecorresponding disk block; responsive to determining at least one virtualblock of another file refers to a given disk block corresponding to afile block in the list, copying the given disk block to generate acopied disk block in the physical disk device; updating a pointer of theat least one virtual block to refer to the copied disk block; andwriting a secure delete pattern for each file block in the list of fileblocks to a disk block in the physical disk device without performingde-duplication processing.
 2. The method of claim 1, wherein writing thesecure delete pattern to the given disk block comprises: responsive to arequest to write to a first virtual block, determining whether the firstvirtual block refers to a first disk block in the ignore list; andresponsive to the first virtual block referring to a first disk block inthe ignore list, writing the secure delete pattern to the first diskblock without performing de-duplication processing on the first diskblock.
 3. The method of claim 2, further comprising: responsive to arequest to write to a second virtual block, determining whether thesecond virtual block refers to a second disk block in the ignore list;and responsive to the second virtual block not referring to a disk blockin the ignore list, performing de-duplication processing on the secondvirtual block.
 4. The method of claim 1, wherein writing the securedelete pattern for each file block in the list of file blocks comprisesat an end of the secure delete operation for the file: for each entry inthe ignore list: calculating a hash value for the corresponding diskblock; removing the entry from the ignore list; and responsive to amatching entry existing in a de-duplication table with a matching hashvalue, adding all virtual blocks referring to the corresponding diskblock in the ignore list to the virtual blocks referring to the diskblock in the matching entry and adding the corresponding disk block asfree in the de-duplication table.
 5. The method of claim 4, whereinwriting the secure delete pattern for each file block in the list offile blocks further comprises at an end of the secure delete operationfor the file: responsive to a matching entry not existing in ade-duplication table, adding the corresponding disk block as allocatedin the de-duplication table with the hash entry and list of virtualblocks referring to the corresponding disk block.
 6. The method of claim1, further comprising: removing each disk block in the list of diskblocks to be securely deleted from a de-duplication table.
 7. A computerprogram product comprising a non-transitory computer readable storagemedium having a computer readable program stored therein, wherein thecomputer readable program, when executed on a computing device, causesthe computing device to: responsive to receiving a secure delete requestfor a file, identify a list of file blocks to be securely deleted from aphysical disk device, wherein identifying a list of file blocks to besecurely deleted comprises creating one or more entries in an ignorelist, wherein each entry in the one or more entries stores a securedelete identifier associated with the secure delete request, a diskblock identifier of a corresponding disk block in the physical diskdevice, and one or more virtual blocks of the file referring to thecorresponding disk block; responsive to determining at least one virtualblock of another file refers to a given disk block corresponding to afile block in the list, copy the given disk block to generate a copieddisk block in the physical disk device; update a pointer of the at leastone virtual block to refer to the copied disk block; and write a securedelete pattern for each file block in the list of file blocks to a diskblock in the physical disk device without performing de-duplicationprocessing.
 8. The computer program product of claim 7, wherein writingthe secure delete pattern to the given disk block comprises: responsiveto a request to write to a first virtual block, determining whether thefirst virtual block refers to a first disk block in the ignore list; andresponsive to the first virtual block referring to a first disk block inthe ignore list, writing the secure delete pattern to the first diskblock without performing de-duplication processing on the first diskblock.
 9. The computer program product of claim 8, wherein the computerreadable program further causes the computing device to: responsive to arequest to write to a second virtual block, determine whether the secondvirtual block refers to a second disk block in the ignore list; andresponsive to the second virtual block not referring to a disk block inthe ignore list, perform de-duplication processing on the second virtualblock.
 10. The computer program product of claim 7, wherein writing thesecure delete pattern for each file block in the list of file blockscomprises at an end of the secure delete operation for the file: foreach entry in the ignore list: calculating a hash value for thecorresponding disk block; removing the entry from the ignore list; andresponsive to a matching entry existing in a de-duplication table with amatching hash value, adding all virtual blocks referring to thecorresponding disk block in the ignore list to the virtual blocksreferring to the disk block in the matching entry and adding thecorresponding disk block as free in the de-duplication table.
 11. Thecomputer program product of claim 10, wherein writing the secure deletepattern for each file block in the list of file blocks further comprisesat an end of the secure delete operation for the file: responsive to amatching entry not existing in a de-duplication table, adding thecorresponding disk block as allocated in the de-duplication table withthe hash entry and list of virtual blocks referring to the correspondingdisk block.
 12. The computer program product of claim 7, wherein thecomputer readable program further causes the computing device to: removeeach disk block in the list of disk blocks to be securely deleted from ade-duplication table.
 13. The computer program product of claim 7,wherein the computer readable program is stored in a computer readablestorage medium in a data processing system and wherein the computerreadable program was downloaded over a network from a remote dataprocessing system.
 14. The computer program product of claim 7, whereinthe computer readable program is stored in a computer readable storagemedium in a server data processing system and wherein the computerreadable program is downloaded over a network to a remote dataprocessing system for use in a computer readable storage medium with theremote system.
 15. An apparatus, comprising: a processor; and a memorycoupled to the processor, wherein the memory comprises instructionswhich, when executed by the processor, cause the processor to:responsive to receiving a secure delete request for a file, identify alist of file blocks to be securely deleted from a physical disk device,wherein identifying a list of file blocks to be securely deletedcomprises creating one or more entries in an ignore list, wherein eachentry in the one or more entries stores a secure delete identifierassociated with the secure delete request, a disk block identifier of acorresponding disk block in the physical disk device, and one or morevirtual blocks of the file referring to the corresponding disk block;responsive to determining at least one virtual block of another filerefers to a given disk block corresponding to a file block in the list,copy the given disk block to generate a copied disk block in thephysical disk device; update a pointer of the at least one virtual blockto refer to the copied disk block; and write a secure delete pattern foreach file block in the list of file blocks to a disk block in thephysical disk device without performing de-duplication processing. 16.The apparatus of claim 15, wherein writing the secure delete pattern tothe given disk block comprises: responsive to a request to write to afirst virtual block, determining whether the first virtual block refersto a first disk block in the ignore list; and responsive to the firstvirtual block referring to a first disk block in the ignore list,writing the secure delete pattern to the first disk block withoutperforming de-duplication processing on the first disk block.
 17. Theapparatus of claim 16, further comprising: responsive to a request towrite to a second virtual block, determining whether the second virtualblock refers to a second disk block in the ignore list; and responsiveto the second virtual block not referring to a disk block in the ignorelist, performing de-duplication processing on the second virtual block.18. The apparatus of claim 15, wherein writing the secure delete patternfor each file block in the list of file blocks comprises at an end ofthe secure delete operation for the file: for each entry in the ignorelist: calculating a hash value for the corresponding disk block;removing the entry from the ignore list; responsive to a matching entryexisting in a de-duplication table with a matching hash value, addingall virtual blocks referring to the corresponding disk block in theignore list to the virtual blocks referring to the disk block in thematching entry and adding the corresponding disk block as free in thede-duplication table; and responsive to a matching entry not existing ina de-duplication table, adding the corresponding disk block as allocatedin the de-duplication table with the hash entry and list of virtualblocks referring to the corresponding disk block.
 19. The apparatus ofclaim 18, wherein writing the secure delete pattern for each file blockin the list of file blocks further comprises at an end of the securedelete operation for the file: responsive to a matching entry notexisting in a de-duplication table, adding the corresponding disk blockas allocated in the de-duplication table with the hash entry and list ofvirtual blocks referring to the corresponding disk block.
 20. Theapparatus of claim 15, wherein copying the given disk block to generatethe copied disk block comprises: getting a free disk block from ade-duplication table as a new disk block; assigning the at least onevirtual block of the another file to the new disk block; and writingdata of the given disk block to the new disk block.